The present invention relates generally to the machine tool art and, more particularly, to an improved heat shrink tool holder cooling cart.
Machine tool holders are used to interface the rotating spindle of a boring or milling machine to a cutting tool that will be used to machine or cut a workpiece. The cutting tool is securely mounted to the tool holder which is then drawn or pulled tightly into the spindle of the machine so as to rigidly maintain the cutting tool within the tool holder and the machine.
It is well known in the art to use heat shrink tool holders for high tolerance machining applications for their ability to mount a cutting tool concentrically within the tool holder. In such tool holders, there is provided a central aperture sized slightly smaller than the diameter of the shank of the cutting tool to be used on the milling or grinding machine. The cutting tool is only insertable into the central aperture when the tool holder has been heated to the temperature necessary to thermally expand the tool holder and consequently the central aperture to a size which can accept the cutting tool shank. Subsequent to the insertion of the shank there into, the tool holder is allowed to cool to the ambient temperature, thereby decreasing the size of the diameter of the central aperture. The thermal contraction of the tool holder and therefore the aperture creates a metal to metal contact between the cutting tool and the tool holder to thereby rigidly secure the cutting tool to the tool holder.
Additionally, machine tool extensions have been formed with heat shrink fittings such that cutting tools are secured to the machine tool extension by the heat shrink process. Such extensions are typically formed with a bore extending axially within one end, with the opposite end of the extension being insertable into the tool holder of a milling or boring machine. Similar to the central aperture of the heat shrink tool holder, the bore of the extension is sized slightly smaller than the shank diameter of the cutting tool. Therefore, the cutting tool shank is only insertable into the bore when the machine tool extension is heated to a temperature sufficient to thermally expand the bore to a size which can accept the cutting tool shank. Subsequent to the insertion of the shank into the bore, the cooling of the extension and the resultant thermal contraction of the bore creates a metal to metal contact between the extension and the cutting tool, thereby rigidly securing the cutting tool to the extension.
However, while the heat shrink tool holder or extension is cooling to ambient temperature, it cannot be used for machining operations because the cutting tool is not rigidly secured to the tool holder. Furthermore, during cooling to ambient temperature, the tool holder is too warm to handle and thus cannot be used. Therefore, after inserting the tool into the heated tool holder, the tool holder must be allowed to cool to ambient temperature in order to provide the strongest union between the cutting tool and tool holder. Only when the tool holder has cooled to ambient temperature can it be used for machining operations. There exist devices to cool heat shrink tool holders and extensions that use a fan or blower for directing the flow of air over the tool holder and thereby capable of cooling the heat shrink tool holder to ambient temperature. Additionally, chillers may also be used to cool heat shrink tool holders to ambient temperature by directing cool air or water over the tool holder. A problem associated with directing cool water over the heat shrink tool holders is the rust as a consequence of iron reacting with oxygen in the presence of water. However, the use of a fan or blower may not be adequate to cool the heat shrink tool holder to ambient temperature expeditiously as may be required during a manufacturing process. Further, the use of a chiller to cool heat shrink tool holders to ambient temperature is difficult to implement in a mobile cooling cart. There exists a need in the art for an improved cooling cart capable of expeditiously cooling heat shrink tool holders to ambient temperature. There also exists a need in the art for a method of cooling heat shrink tool holders using a cooling process utilizing both convection and conduction.
The present invention addresses the deficiencies in prior art coolers by providing a cooler that uses a chiller and pump to circulate cool water into a water tank to therefore cool the tool holders by a thermal conduction method. Therefore, the present invention provides a cooler unit capable of cooling heat shrink tool holders or extensions to ambient temperature with or without requiring the use of a fan or blower to propel ambient temperature air over the heated tool holders.